To meet customer demands, image output devices such as a printer or display need to produce a consistent spectrum of colors over time. For example, customers want a printing system to produce a particular colored document consistently from day to day, or print job to print job.
To control the color rendering consistency of a printing device, the printing device is typically characterized and calibrated prior to being shipped to a customer. The characterization process produces a set of LUTs (look-up tables) which correlate a standardized set of target colors with the appropriate device dependent color space values necessary to produce the target colors with the printing device. For example, a Pantone.RTM. color spectrum may be utilized as a color target reference and the LUTs produced by the characterization process are device dependent CMYK color space representations of the Pantone.RTM target colors. More commonly the target colors are selected based on transforming a uniformly sampled RGB grid to L*a*b* space using suitable RGB to L*a*b* transformation. The device dependent CMYK color space values are found for each of the nodes in the transformed L*a*b* space using Gray Component Replacement, inversion and gamut mapping algorithms. The characterization process is generally referred to as profiling a device or printer. The calibration process is used to build 1-dimensional tone reproduction curves and is carried out more frequently than the characterization process.
To accomplish the profiling of a printing device, a spectrophotometer or other image sensing device is used to measure the calorimetric properties of the produced images. These measured calorimetric properties provide an objective basis of comparison to the reference target color set and provide the necessary feedback to iteratively generate accurate device dependent LUTs.
Notably, the device profiling method discussed above can also be applied to a display where an image sensing device is approximately located to the display for calorimetric measurements of the displayed image. In addition, multiple LUTs may be generated for an image output device to account for multiple media types and/or half tone screens.
This disclosure relates to image output device color management methods and systems. Specifically, this disclosure provides methods and systems to create profiles for preference color matching.